File systems are often stored on data volumes created by storage devices (e.g., disk arrays). Data volumes are viewed as a sequence of logical memory blocks that store file system data. Typically, all data volume blocks are equal in size, although this disclosure should not be limited to blocks of equal size. While it is said that a volume stores data, in reality, the data is actually stored directly or indirectly in physical memory blocks of a storage device (e.g., a disk array) that are allocated to the volume blocks.
Snapshot copies of data volumes are created to guard against data corruption. A snapshot is a copy of the data volume as it existed at a point-in-time. In the event of data corruption as a result of user, software, or hardware error, a snapshot copy can be used to restore the corrupted data volume back to a consistent data state that existed at the time the snapshot copy was created.